1. Field of the Invention
This invention relates to machines for forming round bales of crop material and has particular reference to the wrapping of bales formed in such machines with a flexible binding material such as conventional bale twine.
2. Description of the Prior Art
It was customary for a great number of years to harvest and store forage crops by mowing the crop in the field, permitting it to dry to a reasonable extent, forming it into windrows, and then compacting the windrows into rectangular bales by conventional hay baling machines. To store rectangular bales, they must either be conveyed to a shed or barn and stacked or, if they are left in a field, they must be covered with waterproof material to prevent rotting.
In recent years, an innovation has occurred in the baling art in the form of a machine which handles the cut crop material in a manner to coil the same into a relatively compact roll, usually of very substantial size and weighing many hundreds of pounds, for example between 1000 and 1500 pounds (455 and 680 kilograms). One of the principal advantages of roll type bales of forage crops is that they may be much more readily stored, as well as fed to herbivorous animals, simply by letting the rolls lie in the field of use or in a feed lot. In this way, animals may readily feed upon such rolls at will and the rolls are self water-shedding and so do not rot.
Several methods of forming of compact rolls of crop material have been devised and one of these involves rolling the swath or windrow of material along the ground until a roll of desired size is obtained. Another, and more successful, method is disclosed in U.S. Pat. Spec. No. 3,815,345 in which a swath or windrow of material is picked up from the field and directed onto a supporting conveyor. This conveyor transports the material in one direction whilst an upper apron, usually positioned above the supporting conveyor, moves in the opposite direction, thereby imparting to the crop material, which it contacts, a circular motion. In an off-the-ground roll forming machine of this type it has been found that to provide optimum weathering characteristics the bale must be rolled and maintained as tightly as possible, consistent with the animals being able to feed off it. The crop material is compacted during the bale forming operation by various types of compression devices which apply pressure to the periphery of the bale as it is being formed. To maintain this compactness, the bale must be secured as tightly as possible when it has been formed to the required size. To this end, the formed bale is wrapped within the machine with a suitable wrapping material such as twine or wire, for example.
For the purpose of illustrating a typical type of apparatus for disposing a roving type strand of wrapping material in a spiral manner around a round bale, attention is directed to U.S. Pat. Spec. No. 3,910,178. In the machine disclosed in this specification, the application of the binding material to the formed roll is at least in part effected manually by an operator sitting, for example, upon the seat of the tractor which propels the machine along a field.
Reference is also made to U.S. Pat. Spec. No. 3,913,473 in which the roving of the wrapping material is effected by an hydraulically-actuated mechanism which moves a twine directing arm substantially in a horizontal plane whilst distributing the wrapping material from the outer end of the arm which moves in an arcuate path between opposite sides of the bale forming machine.
Some of the prior art wrapping material dispensing mechanisms are of the rope-controlled type. Such mechanisms are pivotally mounted on a support and are movable back and forth in an arcuate path in the vicinity of the bale forming region in the machine. Spring means extending between the mechanism and a fixed member of the machine frame urge the mechanism in one direction along said arcuate path whilst the rope attached to the mechanism allows the operator to pull the mechanism in the opposite direction along said path. Such rope-controlled pivotal dispensing mechanisms are very simple in design and cheap in construction but they have some disadvantages one of which will briefly be explained hereafter. In operation, wrapping material is fed through the twine dispensing mechanism as it is pivoted back and forth across the bale forming region and the material is thus spirally wound around the bale which is rotated within the machine. Because of the relative motion between the dispensing mechanism and the bale, the wrapping material lags the dispensing mechanism as it is wound around the bale. This results in a certain pulling force on the dispensing mechanism which aids movement of the latter at some parts of the path of movement, and opposes at other parts. Usually this causes no problems during the return stroke of the dispensing mechanism, i.e. the stroke induced by the operator pulling on the rope, but problems may occur in a last portion of the forward stroke since motive power at this time is provided by spring means and may be insufficient to overcome the pull on the twine by the lag effect. If so, the dispensing mechanism fails to reach its extreme position at the end of the forward stroke, or hesitations in the pivotal movement occur.